This invention relates to chemical mechanical planarization (CMP) for Shallow Trench Isolation (STI) process. More specifically, the present invention is directed to methods or processes of reducing (treating) trace metal contaminants and smaller or fine sized cerium oxide particles in cerium oxide particles or cerium oxide slurry and in STI polishing compositions.
Chemical mechanical polishing (CMP) compositions for Shallow Trench Isolation (STI) generally contain abrasive such as cerium oxide particles or colloidal cerium oxide particles, and suitable dispersing agents.
For example, U.S. Pat. No. 5,876,490 discloses the polishing compositions containing abrasive particles and exhibiting normal stress effects. The slurry further contains non-polishing particles resulting in reduced polishing rate at recesses, while the abrasive particles maintain high polish rates at elevations. This leads to improved planarization. More specifically, the slurry comprises cerium oxide particles and polymeric electrolyte, and can be used for Shallow Trench Isolation (STI) polishing applications.
As another example, U.S. Pat. No. 6,964,923 teaches the polishing compositions containing cerium oxide particles and polymeric electrolyte for Shallow Trench Isolation (STI) polishing applications. Polymeric electrolyte being used includes the salts of polyacrylic acid, similar as those in U.S. Pat. No. 5,876,490. Ceria, alumina, silica & zirconia are used as abrasives. Molecular weight for such listed polyelectrolyte is from 300 to 20,000, but in overall, <100,000.
However, those Shallow Trench Isolation (STI) polishing compositions usually contain trace metal contaminants, that are known to cause defects in a STI CMP process. The trace metal contaminants include, but not limited, to Al, Zr, Fe, Ni, Mg and others.
In addition, very small and fine cerium or colloidal cerium oxide particles in the STI polishing compositions are also known to cause defects in a STI CMP process.
Thus, there is still a need for Shallow Trench Isolation (STI) polishing compositions that provide reduced trace metal contaminants; and reduced very small and fine cerium oxide particles to achieve reduced defects in a STI chemical and mechanical polishing (CMP) process.